Dough viscoelastic response of hydrocolloid/enzyme/surfactant blends assessed by uni- and bi-axial extension measurements

The effects of two hydrocolloids-hydroxypropylmethylcellulose (HPMC) and a high ester pectin (BIG)-on the uni- and bi-axial extensional profile of wheat flour doughs when used singly and in combination with amylolytic (alpha-amylase, NMYL), non-amylolytic enzymes (transglutaminase. TGM and xylanase, PTP) and an emulsifier (diacetyl tartaric acid ester of mono-diglycerides, DATEM) have been investigated by applying response surface analysis to a Draper-Lin small composite design of formulated dough sanples. Significant relatioships between uni- and bi-axial extensional parameters were observed. Quadratic effects of BIG (2% flor basis) were particularly significant (%) in increasing extensibility at rupture (+22%) and maximum extensibility (+32%), and stress at end of relaxation period (+130%). DATEM addition that magnified changes observed for maximum extensibility induced a quadratic positive effect on strain hardening index that increased by 9% when surfactant is added at 0.8%, flour basis. DATEM and BIG that have not single and/or quadratic effects on tenacity, increased the viscous component by 37% when added together. A significant single and positive effect of TGM on time of semirelaxation was observed. Suitable rheological trends to perform a high quality bread-optimal resistance to uni- and bi-axial extension, high extensibility before break/stretching, great strain hardening in bi-axial extension, and longer time of semirelaxation-were achieved by adding BIG/DATEM/TGM into dough formula. In spite of the beneficial strengthening effect of HPMC alone, caution should be paid to mixtures BIG/HPMC due to antagonistic effects of both hydrocolloids and subsequent decrease on both tenacity and extensibility at bubble rupture that may cause premature rupture of the membranes between the gas cells, and consecuently a loss of gas. (C) 2003 Elsevier Ltd. All rights reserved.